The present invention relates to an automatic circuit breaker switch, which utilizes a bimetallic blade, a push button to make a circuit and a push rod to break a circuit.
Known circuit breakers have employed a bimetallic contact that flexes when excessive current flows through it. This flexing can release a spring loaded push button to separate contacts and open a circuit. Such arrangements are noted for its simplicity and reliability. To add flexibility, known circuit breakers have included a separate manual push rod or lever to open the contacts manually.
In U.S. Pat. No. 5,001,450, a circuit breaker has a push button with a lateral tab. The tab can be spring biased against the side of a pair of electrical contacts. One of the contacts is supported by a bimetallic blade, which lifts the contact when excessive current flows. When the contacts thus separate, the lateral tab of the push button is driven by its spring to a position between the contacts, keeping them open even when the bimetallic element cools. An alternate way of opening the contacts is provided by a push rod having a bevelled inside end. The bevel can engage the underside of an extended portion of the bimetallic blade. One disadvantage with this known circuit breaker is the need to extend the bimetallic blade simply to accommodate the push rod that can manually break this circuit. Additionally, the bevelled end of the push rod not only applies a force that lifts and separates the contacts, but also a force transverse to the contacts that tends to twist and misalign the bimetallic blade and the contacts. Also with the higher forces necessary to operate a bevelled push rod, there is a greater tendency for wear and jamming.
Other known bimetallic circuit breakers employ manual devices to open the circuit, but these have disadvantages as well. These known manual devices either operate indirectly and require additional material or mechanisms; or operate at an inefficient angle which increases the force necessary to break a circuit. For switches having circuit-making push buttons that are parallel to circuit breaking push rods, see: U.S. Pat. Nos. 1,784,207; 1,928,940; 2,767,281; 2,768,262; 2,824,932; and 2,952,757. Other bimetallic switches are shown in U.S. Pat. Nos. 3,211,862; 4,044,325; 4,570,142; and 4,573,031.
Accordingly, there is a need for a bimetallic circuit breaker having a push button to make and a push rod to break a circuit, which are arranged to operate efficiently and without excessive forces and friction.